[libFuzzer] Use octal instead of hex escape sequences in PrintASCII

Previously, PrintASCII would print the string "\ta" as "\x09a". However,
in C/C++ those strings are not the same: the trailing 'a' is part of the
escape sequence, which means it's equivalent to "\x9a". This is an
annoying quirk of the standard. (See
https://eel.is/c++draft/lex.ccon#nt:hexadecimal-escape-sequence)

To fix this, output three-digit octal escape sequences instead. Since
octal escapes are limited to max three digits, this avoids the problem
of subsequent characters unintentionally becoming part of the escape
sequence.

Dictionary files still use the non-C-compatible hex escapes, but I
believe we can't change the format since it comes from AFL, and
libfuzzer never writes such files, it only has to read them, so they're
not affected by this change.

Differential revision: https://reviews.llvm.org/D110920
This commit is contained in:
Hans Wennborg 2021-10-01 10:59:55 +02:00
parent 4288b6520a
commit c7bd643599
4 changed files with 49 additions and 1 deletions

View File

@ -23,6 +23,14 @@ namespace fuzzer {
static FILE *OutputFile = stderr;
FILE *GetOutputFile() {
return OutputFile;
}
void SetOutputFile(FILE *NewOutputFile) {
OutputFile = NewOutputFile;
}
long GetEpoch(const std::string &Path) {
struct stat St;
if (stat(Path.c_str(), &St))

View File

@ -54,6 +54,10 @@ void DupAndCloseStderr();
void CloseStdout();
// For testing.
FILE *GetOutputFile();
void SetOutputFile(FILE *NewOutputFile);
void Printf(const char *Fmt, ...);
void VPrintf(bool Verbose, const char *Fmt, ...);

View File

@ -43,7 +43,7 @@ void PrintASCIIByte(uint8_t Byte) {
else if (Byte >= 32 && Byte < 127)
Printf("%c", Byte);
else
Printf("\\x%02x", Byte);
Printf("\\%03o", Byte);
}
void PrintASCII(const uint8_t *Data, size_t Size, const char *PrintAfter) {

View File

@ -591,6 +591,42 @@ TEST(FuzzerUtil, Base64) {
EXPECT_EQ("YWJjeHl6", Base64({'a', 'b', 'c', 'x', 'y', 'z'}));
}
#ifdef __GLIBC__
class PrintfCapture {
public:
PrintfCapture() {
OldOutputFile = GetOutputFile();
SetOutputFile(open_memstream(&Buffer, &Size));
}
~PrintfCapture() {
fclose(GetOutputFile());
SetOutputFile(OldOutputFile);
free(Buffer);
}
std::string str() { return std::string(Buffer, Size); }
private:
char *Buffer;
size_t Size;
FILE *OldOutputFile;
};
TEST(FuzzerUtil, PrintASCII) {
auto f = [](const char *Str, const char *PrintAfter = "") {
PrintfCapture Capture;
PrintASCII(reinterpret_cast<const uint8_t*>(Str), strlen(Str), PrintAfter);
return Capture.str();
};
EXPECT_EQ("hello", f("hello"));
EXPECT_EQ("c:\\\\", f("c:\\"));
EXPECT_EQ("\\\"hi\\\"", f("\"hi\""));
EXPECT_EQ("\\011a", f("\ta"));
EXPECT_EQ("\\0111", f("\t1"));
EXPECT_EQ("hello\\012", f("hello\n"));
EXPECT_EQ("hello\n", f("hello", "\n"));
}
#endif
TEST(Corpus, Distribution) {
DataFlowTrace DFT;
Random Rand(0);